Pneumatic stapling tool



April 9, 1963 J. H. DALTON PNEUMATIC STAPLING TOOL 2 SheetsSheet 1 Filed May 16, 1960 April 1963 J. H. DALTON 3,084,672

PNEUMATIC STAPLING TOOL &

INVENTOR: 4%

1 W R My;

W Wf Delaware Filed May 16, 1960, tier. No. 29,536

4 Claims. or. 121-2i) The present invention relates to improvements in pneumatic stapling tools, and in particular to a new and improved air valve and piston-cylinder combination.

Pneumatic stapling tools include an air cylinder, a piston reciprocable in the cylinder and arranged for powering a staple driver, a magazine for storing staples and having means for feeding staples to be driven by the staple driver into the work, an air valve for controlling the flow of air into and the exhaust of air from, the cylinder, a trigger for manipulating the valve, and a spring for returning the piston to the top of the cylinder. Some pneumatic staplers are also provided with means for temporarily detaining the piston from its power stroke for an instant after the valve has opened in order to permit build up of air pressure at the piston head to overcome the resistance of the return spring and to insure a rapid and sharp stroke of the staple driver.

A principal object of the present invention is to provide in a pneumatic stapling tool a new and improved combination of air cylinder, piston, and valve for controlling the supply of air to the cylinder during the stapling stroke and the return stroke.

Another object is to provide in a pneumatic stapling tool a new and improved combination of an air valve and a piston which is reciprocated without the use of a hold-up means prior to the power stroke or a spring or similar means for the return stroke.

Another object is to provide a new and improved control valve for pneumatically operated tools which has its operation controlled by a manually operable pilot valve.

Another object is to provide a new and improved control valve for pneumatically operated tools which is opened by air pressure, the application of which is controlled by a manually operable pilot valve, thereby reducing the manual effort needed to open the valve over conventional air valves.

Other objects and advantages will become apparent from the following description taken in conjunction with the accompanying drawings, wherein FIG. 1 is a fragmentary medial longitudinal sectional view of a pneumatically operated stapling tool incorporating the air valve and piston-cylinder combination of the present invention;

FIG. 2 is a view similar to FIG. 1, but showing the air valve fully opened and the piston at the end of its power stroke;

FIG. 3 is an irregular horizontal sectional view taken along the line 3-3 of FIG. 1, looking in the direction of the arrows;

FIG. 4 is a horizontal sectional view taken along the line 4-4 of FIG. 1, looking in the direction of the arrows; and

FIG. 5 is an enlarged detail sectional view of the air valve taken along the line 55 of FIG. 1, looking in the direction of the arrows.

The present invention is illustrated and described in conjunction with a pneumatic stapling tool of the type shown and described in greater detail in the patent to Arvid I. Ericsson, No. 2,947,003, dated August 2, 1960', entitled Pneumatic Stapling Tool. It is to be understood, however, that the principles of this invention may be applied to other pneumatically operated, manually triggered tools, where high impact is desired.

The pneumatic stapling tool in which the present invenatent ice tion is incorporated is indicated generally by the reference character 10 and includes a main body casting 12 providing a handle portion 14 and an air cylinder 16, and a staple magazine 18 suitably secured to the casting 12. In the handle portion of the casting there are formed an air inlet passage 20, and an air exhaust passage 22, the inlet passage 20 being tapped at its outer or inlet end 24 to receive a fitting to which the conventional air supply hose (not shown) may be connected. The flow of air to and from the cylinder 16 is under the control of an air valve 25. The tool also includes a nose assembly 26 at the forward end of the magazine 18 and below the air cylinder 16, which is adapted to be held against the work and through which the staples are driven.

The upper end of the cylinder 16 is closed by a cap 28 formed with a plurality of stops 30 against which a doubleheaded piston 32, reciprocable in the cylinder 16, bears when in retracted position. A staple driver blade 34 is connected to the piston generally in the manner described in Harold F. Baker Patent No. 2,881,738, issued April 14, 1959, entitled Piston and Staple Driver Combination." The piston 32 is cylindrical and has a bore 31 extending thereinto from its upper end. The bore 31 is threaded at its upper end and is closed by a tapped and kerfed plug 29. A sleeve 27 is confined between the underside of the plug 29 and the bottom of the bore 31 and is internally threaded at 33 adjustably to receive and hold the upper end of the driver blade as taught in the aforementioned Baker patent. The lower portion of the blade 34 extends through a bore 35 communicating with the bore 31 and which has diametrically opposite recesses 37 (FIG. 3) projecting into the lower portion of the piston to accommodate the side edges of the driver blade which is wider than the diameter of the bore 34. Thus, the blade 34 is inhibited against rotational movement beyond a few degrees relative to the piston 32, and the axial positioning of the blade 34 and piston 32 will remain substantially constant during tool usage. Furthermore, this structure will permit the use of driver blades 34 of varying widths with the same piston provided the magazine and nose assemblies 18 and 26 are changed to accommodate the different conditions.

A ring cushion 36 is positioned in the lower end of the cylinder 16 to absorb the impact of the piston 32 should the tool be operated with little or no resistance, as in the case of testing by firing into the air, or by driving a staple into an object having little resistance. The cushion 36 is retained in an inturned flange 38 at the lower end of the cylinder 16.

As best seen in FIG. 1, the piston 32 is double headed and has its upper or head portion 40 formed with a larger diameter than its body. An annular groove 42 is formed in the upper piston portion 40 and retains an O-ring 44 which seals against the wall of the cylinder 16 in upper portion 41 thereof. Directly below the upper or head piston portion 40 is a sealing portion 46 which has a diameter slightly smaller than that of the upper portion but larger than the diameter of the major and intermediate or waist portion 47 of the piston body. A shoulder 43 is defined between the head portion 40 and sealing portion 46, and another shoulder 45 is defined between the sealing portion 46 and intermediate portion 47. An annulus 48 at the bottom of the piston, equal in diameter to the sealing piston portion 46, forms the lower piston head and defines with the intermediate portion 47 a shoulder 53 equal in area to the shoulder 45. This lower head 48 is slidable in cylinder portion 49 which is only slightly larger in diameter than the lower piston head 48 and lies below sealing ring 50 fixed in annular groove 51 in the wall of the cylinder 16 about the longitudinal midpoint thereof and below a shoulder 52 connecting the upper cylinder portion 41 with the lower cylinder portion 49. The ring 50' is adapted to seal against the lower piston annulus 48 when the piston 32 is retracted and against the sealing portion 46 when the piston is at the end of its power stroke. It does not sealagainst the intermediate and major portion 47 of the piston. The various piston shoulders define dilferential areas which function in retracting the piston 32 from the end of its power stroke (FIG. 2

Ports 54 are defined between the stops 30 in the cap 28 and communicate the interior of the cylinder 16 at its head end with an annular passage 56 and an angular passage 58 which leads toward the air control valve 25, the air inlet passage 20, and the exhaust passage 22. A second angular passage 60 connects the air inlet passage 20 to the upper portion 41 of the cylinder 16 slightly above the sealing ring 50 and the cylinder shoulder 52.

The air control valve 25, which is constructed in accordance with the present invention, is located within a cored passageway '64which lies between the inlet and outlet passages 20 and 22, and the angular passage 58. The valve 25 includes a valve sleeve 66 which has a tight fit in the passageway 64, is sealed against air leakage by a pair of gaskets 68, and is held against rotation and removal by a rolled retaining pin 70. The valve sleeve 66 is tapped at both ends and has a shouldered central portion 72 defining a valve cavity 71 thereabove land a cylinder '73 therebelow. A port 79 in the central portion 72 communicates the valve cavity with the cylinder, and it is circumscribed at its upper or valve cavity end with a valve seat 74 formed on the sleeve portion 72.

A port 76 in the valve sleeve 66 connects the valve cavity 71 with the angular passage 58 leading to the head end of the cylinder 16. An exhaust port 78in the sleeve 6*61below the central dividing portion 72 communicates the valve cylinder 73 'with the exhaust passage 22. Thus, when the valve 25 is closed, as shown in FIGS. 1 and 5, the head end of the cylinder is vented to atmosphere through the ports 54, passage 58, port 76, valve cavity 71, port 79, valve cylinder 73, exhaust port '78, and exhaust passage 22.

Hollow plugs 80 and '82 are secured in the upper and lower ends, respectively, of the valve sleeve 66 and are sealed thereagainst by O-rings 84. An inlet port 83 in the plug 80 connects the air inlet passage 20 with the valve cavity 71, and at its inner end the port 83 is circumscribed by a valve seat 86 formed on the lower edge of the plug 80 and spaced slightly away from the wall of the valve cavity 71. The lower plug 82 has a bore 81 therethrough which terminates at its upper and inner end in a conical valve seat 88.

A pilot valve member 90 has a stem 91 slidably projectingthrough the bore 81 of the plug 82. The valve member 90 has a head 92 below which is an annular groove 93 in which is fitted an O-ring 94 which is adapted to seal against the conical valve seat 88. Vertical flutes 96 traverse the major portion of the length of the valve stem 91, terminating slightly below the groove 93, and communicate or vent the cylinder 73 with the atmosphere when the valve member is pressed inwardly of the sleeve 66.

A main valve member 98 is reciprocably positioned in the valve sleeve 66 and has an upper valve portion 100 and a lower piston portion 102 interconnected by a stem 104. The stem 104 has a bore 108 therethrough which is threaded at its upper [end 106. The bore 108 communicates with a larger counterbore 110 in the piston portion 102 of the main valve member 98. A spring 1 12 has its upper end confined in the counterbore 110 and its lower end pressing on the sealing ing 94 of the pilot valve member 90'. The action of the spring is such as to bias the pilot valve member 90 to closed position against the conical valve seat 88 and the main valve member 98 to closed position against the valve seat 86. An O-ring 114 seals the valve piston portion 102 against the wall of the valve cylinder 73 below the outlet port 78.

A screw 116 is threaded into the tapped portion 106 of the stem 104 and holds tightly in place beneath its head a ferrule 118 having an outwardly facing groove 119 into which is fitted an O-ring 120 which is adapted to seal against the upper valve seat '86 and the lower valve seat 74 at the limits of movement of the valve member 98. A small gasket 122 seals between the lower face of the ferrule 118 and the upper face of the stem 104. The screw 116 has a bore 117 therethrough which communicates the port 83 and the air inlet passage 20' with the bore 108, counterbore 110, and valve cylinder below the valve piston 102 to add air pressure to the pressure of the spring in holding the main valve member 98 against the valve seat 86 and the pilot valve member against the conical valve seat 88 It is to be noted that in both extreme positions of the valve member 98 the cylinder 73 above the piston isat atmospheric pressure through the port 78 andpassage 22. The valve member 90 is opened by an upward pressure on the projecting end of its valve stem 91 to lift the sealing ring 94 from the valve seat 88.. This upward pressure or force is applied through a trigger 124 which is pivoted on a pin 126 to the casting 12 in a slot 125 adjacent the lower end of the cylinder 16. A pin 128 limits the movement of the trigger in the clockwise direction.

When the pilot valve is opened the air pressure in the cylinder 73 below the valve piston 102 is dropped through the spaces defined by the bore 81 and the flutes 96 on the valve stem 91 and the air pressure acting on the head or" the valve portion 11301 exceeds the total pressures, air and spring pressures, acting on the valve piston 102 so that the valve portion is moved from its position against the valve seat 86 to its position against the valve seat 74, thus communicating the head of the piston 32 with air under inlet pressure to drive it from the position 1gfGFIG. 1 through its power stroke to the position of On the power stroke of the piston 32 the driver blade 34-strips a staple 130*from the staple stick in the magazine 4 8 and drives it through the guideway in the nose assembly and into the work.

The operation of the stapling tool of this invention is as follows. Assume that the valve 25 is closed with the main valve member 98 -sealed against the valve seat 86, and the pilot valve member 90* sealed against the valve seat 88, that the piston 32 is in its upper or retracted position (FIG. 1), and that a staple 130' is positioned in the staple guideway beneath the driver blade 34. Air under pressure has entered the valve assembly 25 through the inlet passage 20, and has passed through the port 83 in the plug 80, the bores 117, 108, and in the valve member 98, and into the valve cylinder 73 below the valve piston 102 to add its pressure to that of the spring 112 to hold the valve member 98 closed against the seat 86. The total pressure on the underside of valve piston 102 is greater, than on the top of the valve portion 100 because of the dilference in surface areas and the etfect of the spring 112. The combined air and spring pressures also hold the pilot valve member 90in closed position against the conical valve seat 88.

With the control valve 25 in this closed position, air under pressure from the inlet passage 20- has passed into the central portion of the cylinder 16 *below the piston head 40-and through the angular passage 60. The piston 32 is, therefore, locked in its retracted position by air under pressure confined in the annular space below the shoulders 43 and45 and sealing ring 44 and above the shoulders 52 and 53 and sealing ring '50: (FIG. 1).

When it is desired to operate the tool, the nose 26 is placed against the work and the trigger 124 is squeezed toward the handle 14 to open the valve 90 against the combined air and spring pressures in the valve cylinder 73, thereby to vent the cylinder through the bore 81 to the atmosphere. This action causes the application of a sudden pressure dilferential between the top and bottom faces of the valve member 98 with the greater pressure being on the top. This greater pressure forces the valve member 98 downwardly against the spring 112, opening the port 83 to the valve cavity 71 and closing the port 79 (FIG. 2).

Air under pressure freely flows from the inlet passage 20 through the port 83, the valve cavity 71, the port 7 6, the angular passage 58, and the ports 54 into the head end of the cylinder above the piston 32. As the top of the head of the piston 32 has an area far greater than the underside of the head 40 above the sealing portion 46, the application of air under the same unit pressure through the passages 58 and 60 will cause the piston to move downwardly on its power stroke. When the lower piston annulus 48 moves off the sealing ring 50, the air under pressure in the annular space about the waist of the piston is vented to atmosphere through the slot 125 and there will be substantially no resistance to the piston movement until the driver 34 strips a staple 130 from the staple stick and drives it into the work. While the piston speed will be an accelerating one the acceleration rate is extremely high and a hammerlike impact drives the staple 130 into the work.

The entire operation of triggering the stapling tool 10 and driving the staple 1130 is very rapid, so that the operator need only squeeze the trigger 1124 and instantaneously release it. Once the trigger is released, the spring 112 closes the pilot valve W and also urges the valve member 98 upwardly. Since the piston 32 is now at the bottom of the cylinder 16 air will no longer flow through the angular passage 58 to the cylinder 16, but will flow through the bores 117, 108, and 110 into the valve cylinder 73 quickly to build up pressure therein to move the valve head 100 quickly to close the port 83 from the valve cavity 71.

Air at inlet pressure flows through the passage 60 into the central portion of the cylinder 16, and below the piston head 40' and the sealing ring 44 to push the piston upwardly. The movement occurs because the total area of the sealing ring 44 and shoulders 43 and 45 greatly exceeds the area of the shoulder 53. As soon as the sealing surface 46 clears the sealing ring th, some air will escape between the waist 47 of the piston and the sealing ring 50, but the area subject to upward pressure (the shoulder 43 and sealing ring 44) being greater than the annular leakage gap (equal to the area of either of shoulder-s 45 or 53) the piston 32 is driven upwardly. The air in the cylinder is forced outwardly through the ports 54, the annular passage 56, angular passage 58, the port 76, the valve cavity 7 1, the port '79, the upper portion of the valve cylinder 73, the exhaust port 78, and the exhaust passage 22. As the piston reaches the top of its return stroke, the O-ring 50 seals against the annulus 48, and air under pressure in the annular space between the piston 32 and the cylinder 16 holds the piston in its retracted position.

It is clear from the foregoing description that the objectives which were claimed for this invention at the outset of this specification, as well as others which have not been specifically set forth, have been fully attained.

While a preferred embodiment of the pneumatic stapling tool constituting the present invention has been shown and described, it will be apparent that numerous modifications and changes may be made therein without departing from the underlying principles of the invention. It is therefore intended, by the following claims, to include all such variations and modifications by which substantially the results of this invention may be obtained through the use of the same or equivalent means.

What is claimed as new and desired to be secured by United States Letters Patent is:

1. In a pneumatic stapling tool for driving staples into a workpiece having an air inlet adapted to be connected to a source of air under pressure, an air exhaust, and a valve assembly controlling the flow of air in through the air inlet and out through the air exhaust, the combination including, means forming a cylinder having upper and lower sections with said upper section having a slightly larger diameter than said lower section, a staple driving piston reciprocable in said cylinder between retracted and advanced positions and having an upper head portion of larger diameter than the remainder of said piston slidable only in said upper cylinder section, lateral port means venting said cylinder to the atmosphere below said upper head portion of said piston when said piston is moved from retracted position, means carried in the wall of said lower cylinder portion for sealing said piston against said lower cylinder section when said piston is in advanced position to define a closed annular space below said piston head, and an unobstructed passage connecting the air inlet with said cylinder at said annular space to furnish air under pressure to said upper cylinder section to move said piston from advanced to retracted position and to hold said piston in retracted position.

2. In a pneumatic stapling tool for driving staples into a workpiece having an air inlet adapted to be connected to a source of air under pressure, and an air exhaust, and a valve assembly controlling the flow of air in through the air inlet and out through the air exhaust, the combination including, means forming a cylinder having upper and lower sections with said upper section having a slightly larger diameter than said lower section, a staple driving piston reciprocable in said cylinder between retracted and advanced positions and having an upper head portion of larger diameter than the remainder of said piston slidable only in said upper cylinder section, lateral port means in said lower cylinder section slightly below the juncture of said upper and lower cylinder sections to vent said cylinder to atmosphere when said piston is moved away from its retracted position, means carried in the wall of said lower cylinder portion above said lateral port means for sealing said piston against said lower cylinder section above said port means when said piston is in either of its extreme positions to define a closed annular space below said piston head, and an unobstructed passage connecting the air inlet with said cylinder immediately above the juncture of said cylinder sections to admit air under pressure to said annular space in said upper cylinder section to move said piston from advanced to retracted position and to hold said piston in retracted position.

3. In a pneumatic stapling tool for driving staples into a workpiece, having an air inlet adapted to be connected to a source of air under pressure, an air exhaust, and a valve assembly controlling the flow of air in through the air inlet and out through the air exhaust, the combination including, means forming a cylinder having upper and lower sections with said upper section having a slightly larger diameter than said lower section, said lower section being vented to the atmosphere below the juncture of said sections, a staple driving piston reciprocable in said cylinder, said piston having an upper head portion slidable in said upper cylinder section, said piston having a lower head portion of smaller diameter than said upper head portion freely slidable in said lower cylinder section and adapted to seal against said lower cylinder section above said vent and below the juncture of said cylinder sections when said piston is in its retracted position, said piston having a sealing portion having a diameter equal to that of said lower head portion and located immediately below said upper head portion to seal against said lower cylinder section when said piston is at the end of its power stroke, said piston having an intermediate portion having a smaller diameter than that of said lower head portion and said sealing portion and interconnecting said last mentioned portions, and an obstructed passage connecting said air inlet with said upper cylinder section immediately above the juncture of said cylinder sections to admit air under pressure to said upper cylinder section to move said piston from advanced to retracted position and to hold said piston in retracted position.

4. In a pneumatic stapling tool for driving, staples into a workpiece having an air inlet adapted to be connected to a source of air under pressure, an air exhaust, and a valve assembly controlling the flow of air in through the air inlet and out through the air exhaust, the combination including, means forming a cylinder having upper and lower sections with said upper section having a slightly larger diameter than said lower section, a sealing ring in the wall of said lower section immediately adjacent the juncture of said upper and lower sections, said lower section being vented to the atmosphere below said sealing ring, a staple driving piston reciprocable in said cylinder, said piston having an upper head portion fitted with a sealing ring to seal against and be slidable in said upper cylinder section, said piston having a lower head portion of smaller diameter than said upper head portion freely slidable in said lower cylinder section and adapted to seal against said first sealing ring when said piston is in its retracted position, said piston having a sealing portion having a diameter equal to that of said lower head portion and located immediately below said upper head portion to seal against said first sealing ring when said piston is at the end'of its power stroke, said piston having an intermediate portion having a smaller diameter than that of said lower head portion and said sealing portion and interconnecting, said last mentioned portions, a passage connecting said air inlet with said cylinder immediately above said first sealing ring to admit air under pressure to said upper cylinder section to move said piston from advanced to retracted position and to hold said piston in retracted position.

References Cited in the file of this patent UNITED STATES PATENTS 574,003 Rinsche Dec. 29, 1896 787,705 Templin Apr. 18, 1905 807,384 Keller Dec. 12,

866,981 Templin Sept. 24, 1907 1,720,705 Waterman July 16, 1929 2,406,747 Davis Sept. 3, 1946 2,687,522 Juilfs Aug. 31, 1954 2,850,738 Campbell et a1 Sept. 9, 1958 2,870,743 Juilfs Jan. 27, 1959 2,872,901 Goldring et a1. Feb. 10, 1959 2,918,675 Smith Dec. 29, 1959 2,931,620 Burns Apr. 5, 1960 2,953,117 Wandel et a1 Sept. 20, 1960 2,954,009 Juilfs Sept. 27, 1960 2,960,067 Osborne Nov. 15, 1960 

1. IN A PNEUMATIC STAPLING TOOL FOR DRIVING STAPLES INTO A WORKPIECE HAVING AN AIR INLET ADAPTED TO BE CONNECTED TO A SOURCE OF AIR UNDER PRESSURE, AN AIR EXHAUST, AND A VALVE ASSEMBLY CONTROLLING THE FLOW OF AIR IN THROUGH THE AIR INLET AND OUT THROUGH THE AIR EXHAUST, THE COMBINATION INCLUDING, MEANS FORMING A CYLINDER HAVING UPPER AND LOWER SECTIONS WITH SAID UPPER SECTION HAVING A SLIGHTLY LARGER DIAMETER THAN SAID LOWER SECTION, A STAPLE DRIVING PISTON RECIPROCABLE IN SAID CYLINDER BETWEEN RETRACTED AND ADVANCED POSITIONS AND HAVING AN UPPER HEAD PORTION OF LARGER DIAMETER THAN THE REMAINDER OF SAID PISTON SLIDABLE ONLY IN SAID UPPER CYLINDER SECTION, LATERAL PORT MEANS VENTING SAID CYLINDER TO THE ATMOSPHERE BELOW SAID UPPER HEAD PORTION OF SAID PISTON WHEN SAID PISTON IS MOVED FROM RETRACTED POSITION, MEANS CARRIED IN THE WALL OF SAID LOWER CYLINDER PORTION FOR SEALING SAID PISTON 